Common Cause Variation vs. Special Cause Variation Key Differences
                     Common Cause Variation vs. Special Cause Variation: Key Differences
It is quite essential to understand variation pertaining to process involvement and quality 
management, for achieving organizational success. Variations are of two types: Common 
Cause variation and Special Cause Variation.
Both types play a significant role that helps determine the stability and performance of 
processes. 
We will explain the key differences 
between the two types of variation with 
the help of real-world examples for a 
better understanding.
1. Common Cause Variation:
2. Special Cause Variation:
Common Cause Variation:
Common cause variation is innate and a natural part of any 
process and its operation. It depicts normal fluctuations that 
occur over time due to factors innate in the process itself. The 
process operates within certain statistical limits under normal 
conditions. Hence, it is stable and predictable.
Examples:
• Daily fluctuations in call volumes at a customer service center.
• Minor variations in product dimensions during manufacturing.
• Variability in delivery times for routine shipments
x
Special Cause Variation:
Special cause variation is caused by an external factor. It is not 
innate in the process and leads to outcomes that are 
unpredictable and uncommon. Special cause variation can lead 
to striking deviations as opposed to expected and stable 
outcomes.
Examples:
• Machine breakdowns leading to production delays.
• Employee errors resulting in quality defects.
• Supplier issues causing disruptions in the supply chain
x
Key Differences
1. Nature
2. Predictability
3. Management Approach
Nature:
• It is innate and a natural part of any process and its operation 
with natural fluctuations
• Special cause variation is caused by an external factor. It is not 
innate in the process.
Predictability:
• Common cause variation is predictable and stable, operating 
within certain statistical limits.
• Special cause variation is unpredictable and can result in 
significant deviations from the expected performance of the 
process..
Management Approach:
• Common cause variation requires process improvements 
and adjustments to reduce variability and enhance stability 
over time.
• Special cause variation requires immediate investigation and 
corrective action to address the root cause and prevent 
recurrence.
Conclusion:
Two types of variation impact process stability: special cause (external 
factors with unexpected effects) and inherent (natural oscillations). 
Effective management practices and understanding these variations 
can optimize performance and drive continuous improvement in 
organizations.
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Closing Slide & Resource:
Resource: https://
www.mindcypress.com/blogs/quality-mana
gement/common-cause-variation-vs-special-
cause-variation-key-differences